In 1846, Navy Secretary George Bancroft issued a General Order stating that “port” would replace “larboard” as a reference to a vessel’s left-hand side, preventing confusion with the similar sounding “starboard”
I've thought that 'port' was designated because in the days of Viking ships that is the side commonly used as the dock side, since the 'steer board' was on the other side of the boat and better kept free to maneuver. And the 'steer board' side because 'starboard' over time . . .